MATLAB: How to update a property of an object of a class with GUI, multi-threading, I presume

guimultiprocessingoop

I'm calling the print_num class from a GUI.
classdef print_num
      properties (SetAccess = private)
          flag = 0;
          n;
      end
      methods
          function obj = print_all(obj, n)
          %PRINT_ALL Prints numbers until interupted
                  obj.flag=0
                  obj.n = n
                  disp('print_num function')
                  i=1        
                  while i<=obj.n
                      if obj.flag == false
                          fprintf('%i flag: %i\n', i, flag)
                          pause(0.1)
                          i=i+1;
                      else
                          break  
                      end
                  end
          end
          function obj = stop(obj)
          %STOP Stop printing of numbers
              disp('Stop function')
              obj.flag=1
          end
      end
  end
I need want to stop the printing of numbers when stop() method is called. I'm calling both the methods print_all(n) and stop() from two pushbuttons of a GUI.
function multiprocessing_OpeningFcn(hObject, eventdata, handles, varargin)
  handles.output = hObject;
  handles.p = print_num;
  guidata(hObject, handles);
% --- Executes on button press in f1.
function f1_Callback(hObject, eventdata, handles)   
  handles.p = handles.p.print_all(20);
  guidata(hObject, handles);
% --- Executes on button press in f2.
function f2_Callback(hObject, eventdata, handles)
  disp('stop called')
  handles.p = handles.p.stop();
  guidata(hObject, handles);
I'm unable to stop the printing of numbers with the flag property of the class print_num. Can someone explain me what I'm doing wrong?

Best Answer

Neel - try deriving your print_num class from the handle class as
 classdef print_num < handle
This will make sure that your obj objects are references to the (same) instantiated object.
Also, rather than using a while loop, you may want to consider using a timer to perform the iterative action. For example,
classdef print_num < handle
    properties (SetAccess = private)
        m_n;
        m_timer = [];
        m_iter;
    end
    methods
        function obj = print_num()
            m_n = 0;
            m_timer = [];
            m_iter = 0;
        end
        function obj = print_all(obj, n)
            if isempty(obj.m_timer)
                obj.m_timer = timer('Name','MyTimer',               ...
                                    'Period',0.1,                   ... 
                                    'StartDelay',0,                 ... 
                                    'TasksToExecute',inf,           ... 
                                    'ExecutionMode','fixedSpacing', ...
                                    'TimerFcn',{@print_num.myTimerCallback, obj});
                obj.m_n = n;
                obj.m_iter = 1;
                start(obj.m_timer);
            end
        end
        function obj = stop(obj)
            if ~isempty(obj.m_timer)
                stop(obj.m_timer);
                obj.m_timer = [];
            end
        end
    end
    methods (Static)
        function myTimerCallback(hTimer, event, objRef)
            fprintf('obj.m_iter = %d\n', objRef.m_iter);
            objRef.m_iter = objRef.m_iter + 1;
        end
    end
end
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